1. Field
The following description relates to an organic light-emitting diode and a flat display device including the same, and more particularly, to an organic light-emitting diode including a multi-layered hole transport layer, wherein the multi-layered hole transport layer is doped with a cyano group-containing compound and a flat display device including the same.
2. Description of Related Art
Organic light-emitting diodes (OLEDs), which are self-emitting devices, have advantages such as a wide viewing angle, excellent contrast, quick response, high brightness, and excellent driving voltage characteristics, and can provide multicolored images.
A general OLED has a structure that includes a substrate, and further includes an anode, a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and a cathode which are sequentially stacked on the substrate. In this regard, the HTL, the EML, and the ETL are organic layers formed of organic compounds.
An operating principle of an OLED having the above-described structure is as follows. When a voltage is applied between the anode and the cathode, holes injected from the anode move to the EML via the HTL, and electrons injected from the cathode move to the EML via the ETL. The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted.
An OLED has not had fully satisfactory characteristics in terms of luminance, efficiency, driving stability, lifetime, and the like, and thus there is an urgent need for development of various improvement technologies. For example, there is a need to develop an OLED having high driving voltage and long lifetime.